A 55-year-old man whith a history of chronic kidney disease comes to the physician due to progressive fatigue, muscle cramps and weakness. His current medications include a vitamin D supplement. While his blood pressure is being obtained, the patient develops carpal spasm. Laboratory evaluation shows a blood urea nitrogen level of 115 mg/dL, serum creatinine level of 8 mg/dL, and serum calcium level of 6.5 mg/dL. Which of the following is most likely contributing to this patient's carpal spasm?

Question

A 55-year-old man whith a history of chronic kidney disease comes to the physician due to progressive fatigue, muscle cramps and weakness. His current medications include a vitamin D supplement.  While his blood pressure is being obtained, the patient develops carpal spasm.  Laboratory evaluation shows a blood urea nitrogen level of 115 mg/dL, serum creatinine level of 8 mg/dL, and serum calcium level of 6.5 mg/dL.  Which of the following is most likely contributing to this patient's carpal spasm?

Quizplus · Accepted Answer

Eductional Objective: In chronic kidney disease, reduced excretion of phosphate can cause hyperphosphatemia.  This induces hypocalcemia directly by binding free calcium and depositing in tissues, and indirectly by triggering fibroblast growth factor 23 secretion (decreases calcitriol production and intestinal calcium absorption).  The resulting hypocalcemia can manifest as neuromuscular excitability (eg, carpal spasm).

A 55-Year-Old Man Whith a History of Chronic Kidney Disease